<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        div{
            width: 200px;height: 200px;
            background-color: pink;
            margin: 0 auto;
        }
        /*关键帧*/
        @keyframes first {
            0%{
                border-radius: 0;
            }
            50%{
                border-radius: 100px;transform: translateX(0);
            }
            100%{
                border-radius: 100px;transform: translateX(100px);
            }
        }
        div:hover{
            animation: first 2s;
        }
    </style>
</head>
<body>
<div></div>
</body>
</html>